The event (which entices members of the press with a promise of “great visuals”) will happen shortly before noon today outside of the White House. The issue spurring such drastic action by Sierra Club director Michael Brune is the proposed Keystone XL pipeline, meaning that Brune will be something like the 1,200th person arrested at the White House protesting that issue.

Brune will be joined by about 50 others, including Bill McKibben of 350.org (and Grist’s board), civil rights leader Julian Bond, Robert Kennedy, Jr., and actress Daryl Hannah (who has been arrested at a White House Keystone protest before). Also included at the event: Randy Thompson, a Nebraska rancher who has emerged as a leader in that state’s fight against the pipeline. According to Fortune magazine, fund manager Jeremy Grantham also plans to participate. “I have told scientists to be persuasive, be brave and be arrested, if necessary, so it only seems proper to do this,” Grantham told the magazine. (Full disclosure: Grantham’s foundation is a funder of Grist.)

The president can’t work miracles by himself. An obstructionist Congress stands in the way of progress and innovation. But President Obama has the executive authority and the mandate from the American people to stand up to the fossil fuel industry, and to reject the Keystone XL tar sands pipeline right now. …

Today we risk arrest because a global crisis unfolds before our eyes. We have the solutions to this climate crisis. We have a moral obligation to stand stand for immediate, bold action to solve climate disruption. We can do it, and we will.

Several years ago, NASA climate scientist James Hansen suggested that building the Keystone XL pipeline would be “game over” for the climate, helping to inspire robust opposition to it from environmentalists. Last January, the president declined to approve the permit needed to build the pipeline across the U.S.-Canada border, following the initial campaign of protests from 350.org and other activists.